chore: extract version from main.go in flake.nix

Use builtins.match to parse version from cmd/homelab-deploy/main.go
so only one location needs updating when bumping versions.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

flake.nix

@@ -15,11 +15,16 @@
       packages = forAllSystems (system:
         let
           pkgs = pkgsFor system;
+          # Extract version from main.go
+          version = builtins.head (
+            builtins.match ''.*const version = "([^"]+)".*''
+              (builtins.readFile ./cmd/homelab-deploy/main.go)
+          );
         in
         {
           homelab-deploy = pkgs.buildGoModule {
             pname = "homelab-deploy";
-            version = "0.1.0";
+            inherit version;
             src = ./.;
             vendorHash = "sha256-JXa+obN62zrrwXlplqojY7dvEunUqDdSTee6N8c5JTg=";
             subPackages = [ "cmd/homelab-deploy" ];